Production of resin impregnated fibrous graphite ribbons

ABSTRACT

A process is provided wherein resin impregnated graphite ribbons may be efficiently produced which may be used in the manufacture of fiber reinforced composite structures. A plurality of multifilament bundles of a fibrous material capable of undergoing graphitization are continuously passed through a graphitization zone from which they are continuously conveyed to and through a coating zone in which they are impregnated with a thermosetting resin. Throughout the continuous process of the invention, the multifilament bundles are provided in an essentially parallel relationship in the form of a ribbon and are continuously passed in the direction of their length. The ribbon product of the invention is particularly suited for use in the formation of strong lightweight composites by filament winding, or other composite forming techniques.

United States Patent Druin 1 1 Mar. 27, 1973 541 PRODUCTION OF RESIN3,412,062 11/1963 Johnson et a1 ..23/209.1 [MPREGNATED FIBROUS GRAPHITE3,108,018 10 1963 Lewis ..117/46 cc RIBBONS Primary ExaminerW1lliam D.Martin [75] Inventor: Melvm Drum west Orange Assistant ExaminerMichaelS. Sofocleous 73 Assignee; (j l Corporation, New York Attorney-Thomas J.Morgan, Charles B. Barris and Kenneth E. Macklin [22] Filed: NOV. 7,1969 57 ABSTRACT [21] Appl' 874,731 A process is provided wherein resinimpregnated graphite ribbons may be efficiently produced which may 52us. (:1. ..ll7/46 CB, 23/2091, 260/37, be used in the manufacture offiber reinforced 2 4 29 7 1 ZB posite structures. A plurality ofmultifilament bundles [51] Int. Cl. ..C01b 31/04 of a fibrous materialcapable of undergoing graphitiza- 58 Field 61 Search 17/46 cc, 46 CB;23/2091; tion are continuously Passed through a graphitization 2 0 37; 24 29 zone from which they are continuously conveyed to and through acoating zone in which they are im- 56 References Cited pregnated with athermosetting resin. Throughout the continuous process of the invention,the multifilament UN S A ES PATENTS bundles are provided in anessentially parallel relationship in the form of a ribbon and arecontinuously passed in the direction of their length. The ribbon3,567,380 3/1971 Townsend; 23/209 4 product of the invention isparticularly suited for use 3,471,322 10 19 9 Medney 7 115 in theformation of strong lightweight composites by 3,323,941 6/1967 VanDijk...,. 117/115 filament winding, or other composite forming 3,214,32410/1965 Peerman ..l17/l61 techniques, 3,367,812 2/1968 Watts 117/46 CC3,235,323 2/1966 Peters ..23/209.1 F 24 Claims, 3 Drawing FiguresPRODUCTION OF RESIN IMPREGNATED FIBROUS GRAPHITE RIBBONS BACKGROUND OFTHE INVENTION In recent years considerable attention has been directedto the production of various fiber reinforced composites. The interestin such composites has been intensified by the demands presented by theaerospace industry for strong lightweight structural materials whichpreferably retain their structural integrity over wide temperatureranges.

As is generally known, a common technique employed in the production ofcomposites involves the filament winding or molding of articles of thedesired configuration utilizing continuous lengths of fibrous materialshaving a coating of a resinous material which ultimately serves as thematrix in the resulting article.

These materials when present in relatively long lengths are commonlydesignated as preimpregnated yarns or tapes or prepreg yarns or tapes.It is, of course, desirable that the preimpregnated fibrous materials exhibit an adequate shelf life to permit transportation and at leastlimited storage prior to use, while being capable of ultimatelyproducing an essentially solid composite structure. Heretofore, thecontinuous lengths of fibrous graphite which serve as the reinforcingmedium have been commonly produced on a batch basis, for instance whilea single end is wound on a suitable frame or support. Subsequently, theresulting lengths of fibrous graphite have commonly been resinimpregnated on a batch basis. There has remained a need for a processfor the efficient formation of high quality resin impregnated graphitetapes or ribbons of substantial length which may be wound to formcomposites exhibiting uniform physical properties.

It is an object of the invention to provide an improved process for theproduction of a resin impregnated graphite ribbon.

It is an object of the invention to provide a continuous process whereinresin impregnated graphite ribbons are expeditiously formed.

It is another object of the invention to provide a process wherein resinimpregnated graphite ribbons of various widths may be convenientlyformed.

It is a further object of the invention to provide a process whereinresin impregnated graphite ribbons are formed which comprisemultifilament graphite bundles having little or no twist aligned in anessentially parallel relationship.

These and other objects, as well as the scope, nature, and utilizationof the invention will be apparent from the following detaileddescription and appended claims.

SUMMARY OF THE INVENTION It has been found that a process for thecontinuous production of a resin impregnated graphite ribbon for use inthe manufacture of fiber reinforced composites comprises:

a. continuously passing a plurality of multifilament bundles of afibrous material capable of undergoing graphitization while in anessentially parallel relationship and in the form of a ribbon through agraphitization zone at a temperature of about 2,000 to 3,l C.(preferably 2,400 to 3,l00 C.) and containing an inert atmosphere for aresidence time sufficient to convert the bundles to graphitic carbonwhile retaining their original fibrous configuration essentially intact,

. continuously feeding the resulting bundles of fibrous graphitic carbonfrom the graphitization zone to a coating zone,

continuously passing the bundles of graphitic carbon through a coatingzone while retaining the essentially parallel relationship of thebundles and the ribbon configuration wherein the ribbon is impregnatedwith a thermosetting resin, and

. withdrawing the resulting resin impregnated graphite ribbon. In apreferred embodiment of the process the multifilament bundles are astabilized acrylic fibrous material which is initially carbonized on acontinuous basis immediately prior to graphitization.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of an apparatusarrangement suitable for carrying out the process of the presentinvention.

FIG. 2 is a side view showing the interior of the induction furnace ofFIG. 1 wherein carbonization and graphitization of a plurality ofmultifilament bundles of a stabilized acrylic fibrous material may becarried out while the bundles are in an essentially parallelrelationship and in the form of a ribbon prior to passing the ribbon tothe coating zone.

FIG. 3 illustrates the configuration assumed by the plurality ofmultifilament bundles as they are positioned upon a roll immediatelyprior to passage through the graphitization zone in an essentiallyparallel relationship and in the form of a ribbon.

DETAILED DESCRIPtION OF THE INVENTION The multifilament bundles offibrous material utilized in the process of the present invention arecapable of undergoing graphitization while retaining their originalfibrous configuration essentially intact. The fibrous bundles treated inthe process may be formed by conventional techniques and may be providedin a variety of physical configurations. For instance, the bundles mayassume the configuration of continuous lengths of multifilament yarns,tows, strands, cables, or similar fibrous assemblages. In a preferredembodiment of the invention the multifilament bundles are lengths of acontinuous multifilament yarn.

The multifilament bundles of fibrous material which are treated in thepresent process may optionally be provided with a twist which tends toimprove the handling characteristics. For instance, a twist of about 0.1to 5 tpi, and preferably about 0.3 to 1.0 tpi may be utilized. Also, afalse twist may be used instead of or in addition to a real twist.Alternatively, one may select bundles of fibrous material which possessessentially no twist. These may be satisfactorily treated in accordancewith the present invention and are particularly suited for theproduction of resin impregnated ribbons for use in compositeapplications where articles of optimum strength are required.

The multifilament fibrous bundles which are graphitized in accordancewith the present process may be carbonaceous (i.e., contain at leastabout percent carbon by weight) and exhibit an essentially amorphousX-ray diffraction pattern. As is known in the art, amorphouscarbonaceous fibrous materials suitable for graphitization may be formedby a variety of techniques. For instance, organic polymeric fibrousmaterials which are capable of undergoing thermal stabilization may beinitially stabilized by treatment in an appropriate atmosphere at amoderate temperature (e.g., 200-400 C.), and subsequently heated in aninert atmosphere at a more highly elevated temperature, e.g., 900 to1,000 C. or more until a carbonized fibrous material is formed whichexhibits an essentially amorphous X-ray diffraction pattern. The exacttemperature and atmosphere utilized during the initial stabilization ofan organic polymeric fibrous material commonly vary with the compositionof the precursor as will be apparent to those skilled in the art. Duringthe carbonization reaction elements present in the fibrous materialother than carbon (e.g., oxygen and hydrogen) are expelled. Suitableorganic polymeric fibrous materials from which the fibrous bundlescapable of undergoing graphitization may be derived include an acrylicpolymer, a cellulosic polymer, a polyamide, a polybenzimidazole,polyvinyl alcohol, etc. As discussed hereafter, acrylic polymericmaterials are particularly suited for use in the formation of thefibrous bundles employed in the present process. Illustrative examplesof suitable cellulosic materials include the natural and regeneratedforms of cellulose, e.g., rayon. Illustrative examples of suitablepolyamide materials include the aromatic polyamides, such as nylon 61,which is formed by the condensation of hexamethylenediamine andterephthalic acid. An illustrative example of a suitablepolybenzimidazoleis poly- 2,2'-m-phenylene-5,5-bibenzimidazole.

A fibrous acrylic polymeric material prior to stabilization may beformed primarily of recurring acrylonitrile units. For instance, theacrylic polymer should contain not less than about 85 mol percent ofrecurring acrylonitrile units with not more than about l5 mol per centof a monovinyl compound which is copolymerizable with acrylonitrile suchas styrene, methyl acrylate, methyl methacrylate, vinyl acetate, vinylchloride, vinylidene chloride, vinyl pyridine, and the like, or aplurality of such monomers.

During the formation of a carbonaceous starting material for use in thepresent process multifilament bundles of an acrylic fibrous material maybe initially stabilized in air (i.e., preoxidized) on a continuous basisin accordance with the teachings of U.S. Pat. application, Ser. No.749,957, filed Aug. 5, 1968, of Dagobert E. Stuetz, which is assigned tothe same assignee as the instant invention and is herein incorporated byreference. More specifically, the acrylic fibrous material should beeither an acrylonitrile homopolymer or an acrylonitrile copolymer whichcontains no more than about 5 mol percent of one or more monovinylcomonomers copolymerized with acrylonitrile. In a particularly preferredembodiment of the invention the multifilament bundles are derived froman acrylonitrile homopolymer. The stabilized acrylic fibrous materialpreoxidized in air is black in appearance, retains its original fibrousconfiguration essentially intact, and is non-burning when subjected toan ordinary match flame. An additional stabilization procedure isdisclosed in commonly assigned U.S. Pat.

application, Ser. No. 865,332, filed Oct. 10, 1969, of Kenneth S. Burnsand William M. Cooper which is herein incorporated by reference.

In the present process the multifilament fibrous bundles of a fibrousmaterial capable of undergoing graphitization are continuously passedthrough a graphitization zone at a temperature of about 2,000 to 3,100C. (preferably 2,400 to 3,l00 C.) which contains an inert atmosphere fora residence time sufficient to substantially convert the bundles tographitic carbon while retaining their original fibrous configurationessentially intact. Suitable inert atmospheres in which thegraphitization reaction may be conducted include nitrogen, argon,helium, etc. For instance, amorphous carbonaceous multifilament bundlesof a fibrous material may be passed through the graphitization zone fora residence time of about 5 seconds to 4 minutes to producegraphitization. Longer graphitization heating times may be selected butgenerally yield no commensurate advantage. Preferred residence times inthe graphitization zone range from about 20 seconds to 120 seconds.

Regardless of their derivation, a plurality of the multifilament bundlesof fibrous material capable of undergoing graphitization arecontinuously passed through the graphitization zone while in anessentially parallel relationship and in the form of a ribbon. Theindividual multifilament bundles are parallel or collimated throughoutthe length of the ribbon, and the ribbon has a flat configuration. Thethickness of the ribbon is essentially that of a single multifilamentbundle. The number of multifilament bundles which are arranged inparallel may be varied depending upon the width of the resin impregnatedribbon desired and the capacity of the graphitization zone. Forinstance, about 4 to 100 or more bundles may be arranged in parallel.

When the multifilament bundles are a stabilized acrylic fibrousmaterial, these bundles may be carbonized as well as graphitized whilein the form of a ribbon in a continuous operation in accordance with theheating schedule of U.S. Pat. application, Ser. No. 777,275, filed Nov.20, 1968, of Charles M. Clarke which is assigned to the same assignee asthe instant invention and is herein incorporated by reference, andsubsequently resin impregnated.

In accordance with this preferred embodiment of the present inventionthe plurality of bundles of stabilized acrylic fibrous material derivedfrom a fibrous material selected from the group consisting of anacrylonitrile homopolymer and acrylonitrile copolymers which contain atleast about mol percent of acrylonitrile units and up to about l5 molpercent of one or more monovinyl units copolymerized therewith arerapidly carbonized on a continuous basis by passage through a heatingzone provided with an inert atmosphere in which their temperature isincreased from within the range of about 20 to 500 C. to a temperaturewithin the range of about 900 to l,600 C. (preferably to a temperaturewithin the range of about l,400 to l,600 C.), within a period of about 3seconds to about 10 minutes, and preferably within a period of 3 secondsto about 5 minutes. Suitable inert atmospheres in which thecarbonization reaction may be conducted include nitrogen, argon, helium,etc.

It accordingly follows in a preferred embodiment of the invention thatsuitable mean heating rates for elevating the ribbon of stabilizedacrylic fibrous material to a temperature of about 1,400 to l,600 C. in

order to produce carbonization range from about 2 to 300 C. per second.In a particularly preferred embodiment of the invention themultifilament bundles are heated to a temperature of about 1,400 toI,600 C. in about to 60 seconds. Particularly preferred mean heatingrates for heating to a temperature of about 1,400 C. to about l,600 C.accordingly range from about 23 to 45 C. per second. The heating ratesemployed need not be constant, but may be varied within the period oftemperature elevation. Particularly satisfactory rates can be achievedwhen the rate is progressively increased. The multifilament bundles ofstabilized acrylic fibrous material undergoing treatment are heated at atemperature within the range of about 900 to 1,600 C. wherein acarbonized ribbon is formed (e.g., for about 3 seconds to about 5minutes), and the resulting carbonized ribbon is subsequentlycontinuously passed through a heating zone provided with an inertatmosphere in which it is heated to a temperature in the range of about2,000 to 3,100 C. (preferably 2,400 to 3,100 C.) for a residence timesufficient to substantially convert the fibrous bundles to graphiticcarbon. The presence of graphitic carbon may be detected by thecharacteristic X-ray diffraction pattern of graphite. Suitable inertatmospheres for use in the graphitization zone include nitrogen, argon,helium, etc. A graphitized ribbon of superior modulus may generally beformedin about 20 to 120 seconds while passing the carbonized bundlesthrough a graphitization zone at about 2,400 to 3,l00 C. Longerresidence times may be selected but generally yield no commensurateadvantage. The modulus of the graphitized ribbon tends to increase withthe maximum temperature achieved during graphitization. The temperatureof the ribbon is preferably progressively increased from a temperaturewithin the range of about 900 to l,600 C. (preferably about l,400 to1,600 C.) to the graphitization temperature of about 2,000 to 3,l00 C.(preferably about 2,400 to 3,I00 C.) within about 2 seconds to about 30seconds.

The equipment utilized to produce graphitization or carbonizationfollowed by graphitization in the present process may be varied widely.It is essential that the apparatus selected be capable of producing therequired temperatures while excluding the presence of an oxidizingatmosphere. For instance, suitable apparatus include induction furnaces,tube furnaces in which a hollow graphite susceptor is heated by directresistance heating, direct resistance heating apparatus in whichelectric current is passed directly through the fibrous material,apparatus capable of producing reducing flames, electric arc furnaces,lasers, thermal image equipment such as solar furnaces, apparatuscapable of producing low temperature plasma flames, and the like. Themultifilament bundles in the form of a ribbon are continuously passedthrough one or more heating apparatus and subjected to the requisitetemperatures to produce a graphite ribbon. Temperature profiles may beprovided within a given heating apparatus or the material may besuccessively passed through a series of apparatus maintained atprogressively increasing temperatures.

In a preferred embodiment of the invention, the bundles undergoinggraphitization or carbonization and graphitization are heated by use ofan induction furnace. In such a procedure the multifilament bundleswhile in the form of a ribbon are passed through a hollow graphite tubeor other susceptor which is situated within the windings of theinduction coil. By varying the length of the graphite susceptor, thelength of the induction coil, and the rate at which the ribbon is passedthrough the susceptor, many apparatus arrangements capable of carryingout the graphitization or carbonization and graphitization may beselected. For large scale production, it is of course preferred thatrelatively long susceptors by used so that the ribbon may be morerapidly passed through the same while being graphitized or carbonizedand graphitized.

During the formation of graphitic carbon within the fibrous bundles ofthe ribbon a tensional force may be optionally applied to the bundlesundergoing graphitization in order to modify the physical properties ofthe same. When a relatively high tensional force is applied in thegraphitization zone, it is preferable that the stress exerted upon theribbon be substantially dissipated prior to its passage through thecoating zone.

The resulting graphite ribbon is continuously fed from thegraphitization zone in which it is formed to a coating zone. Thecontinuous transport of the graphite ribbon to the coating zone may befacilitated by passing the same over rotating rollers, or through theuse of other techniques which will be apparent to those skilled in fibertechnology. The coating zone is preferably positioned in relativelyclose proximity to the graphitization zone so that the coating step maybe carried out in an efficient manner without undue delay.

The graphite bundles while in an essentially parallel relationship andin the form of a ribbon are impregnated with a thermosetting resin whilebeing continuously passed through the coating zone. The thermosettingresin may be applied to the continuously moving graphite ribbon by avariety of techniques. For instance, the ribbon may be immersed ordipped in a suitable resin bath having a liquid consistency while beingpassed through the coating zone. Alternatively, the liquid thermosettingresin may be applied to the graphite ribbon during its passage throughthe coating zone by padding, spraying, or any other convenienttechnique. The coating technique selected should be such that theindividual filaments making up the multifilament bundles are notappreciably damaged during the coating procedure, or the ribbonconfiguration of the bundles disturbed.

The thermosetting resin which is applied to the graphite ribbon in thecoating zone is of liquid consistency, and may be applied from either asolvent or a solventless system. When a solventless system of athermosetting resin is selected for use in the process, the graphiteribbon is preferably coated in accordance with the teachings of U.S.Pat. application, Ser. No. 791,033, filed .Ian. 14, 1969, of Ramesh R.Desai, which is assigned to the same assignee as the present inventionand is herein incorporated by reference. A solventless system comprisingan A-stage thermosetting resin is preferably utilized and is maintainedat a temperature of about 20 to C. immediately prior to its applicationto the graphite ribbon. In a particularly preferred embodiment of theinvention the solventless system comprising an A-stage thermosettingresin is maintained at a temperature of about room temperature (e.g.,about 25 C.) in order to optimize its pot life or period of usefulnessprior to its application to the ribbon.

The solventless system comprising an A-stage thermosetting resin isflowable and the thermosetting resin is essentially uncured. Such resinwhen exposed to heat hardens or sets to a rigid solid consistencydesignated as a C-stage thermosetting resin, and may not subsequently berendered plastic or flowable upon the reapplication of heat. The curingor hardening of the thermosetting resin is brought about byheat-promoted chemical changes which result in the formation of acompact, often cross-linked system. It is accordingly essential thatgraphite ribbon coated with such thermosetting resins be molded orshaped to form composites of the desired configuration prior to thepoint in time when the curing reaction has progressed to the C- stage. AB-stage thermosetting resin is defined as a partially curedthermosetting resin which has neither the consistency of a flowableliquid, nor the consistency of a rigid solid. A B-stage thermosettingresin is accordingly soft and tacky in its consistency and may bereadily molded. Upon the passage of time even at room temperature aB-stage thermosetting resin will assume a C-stage consistency. Thisconversion from a B-stage consistency to a completely gelled C-stageconsistency is accelerated or advanced by heat. The solventless systemapplied in the coating zone may comprise the A- stage thermosettingresin, one or more curing agents for said thermosetting resin, and oneor more accelerators.

When the thermosetting resin is applied from a solvent system, the resinis dissolved in a solvent capable of dissolving the same to form aflowable liquid. Suitable solvents which are commonly utilized in suchsolvent systems include acetone, methyl ethyl ketone, dimethyl ketone,perchloroethylene, methylene chloride, ethylene dichloride, dimethylformamide, etc. The thermosetting resin dissolved in the solvent may beeither uncured or partially cured (i.e., advanced). The

composite structure. If desired, various modifiers or diluents of thereactive type also may be present within either the solventless or thesolvent thermosetting resin systems. Such components form a permanentportion of the hardened thermosetting resin, and do not evaporate fromthe same during the curing reaction.

The thermosetting resin applied to the graphite ribbon in the coatingzone may generally be selected from those thermosetting resins utilizedin the production of fiber reinforced composites by prior arttechniques. It is, of course, necessary that a thermosetting resin beselected which is either inherently liquid at the coating temperature orwhich may be modified to possess flowable properties at the coatingtemperature by the addition of a reactive modifier or diluent, or bydissolution in a solvent for the same. Illustrative examples of suitablethermosetting resins for use in the present process for the productionof resin impregnated graphite ribbons include epoxy resins, phenolicresins, polyester resins, polyimide resins, etc.

An epoxy resin is the preferred thermosetting resin for use in theprocess of the present invention. The epoxy resins utilized in thepresent invention are most commonly prepared by the condensation ofbisphenol A (4,4' isopropylidene diphenol) and epichlorohydrin. Also,other polyols, such as aliphatic glycols and novolac resins, acids orother active hydrogen containing compounds may be reacted withepichlorohydrin for the production of epoxy resins suitable for use inthe instant process provided resins are selected which possess or can bemodified to possess the requisite flow properties. Numerous reactivediluents or modifiers which are capable of increasing the flowproperties of uncured epoxy resins are well known and include butylglycidyl ether, higher molecular weight aliphatic and cycloaliphaticmonoglycidyl ethers, styrene oxide, aliphatic and cycloaliphaticdiglycidyl ethers, and mixtures of the above.

In a preferred embodiment of the invention epoxy resins are selectedwhich possess terminal epoxide groups and are condensation products ofbisphenol A and epichlorohydrin of the following formula:

solvent component of the solvent system may be removed from the resinimpregnated graphite ribbon either before or during its ultimatefabrication into a fiber reinforced composite. For instance, the solventmay be conveniently removed from the resin impregnated graphite ribbonby subjecting the same to moderate heating, such as by passing the resinimpregnated graphite ribbon through an additional heating zone whilepreserving its ribbon configuration. If solvent remains in the graphiteribbon at the time it is molded, it is preferable that the mold usedduring the formation of a composite structure be of the open typewhereby the solvent may escape from the same without producing voids inthe resulting article. Substantially all of the curing of thethermosetting resin may occur during or after the ultimate formation ofa where n varies between zero and a small number less than about 10.When n is zero, the resin is a very fluid light-colored material whichis essentially the diglycidyl ether of bisphenol A. As the molecularweight increases so generally does the viscosity of the resins.Accordingly, the particularly preferred liquid epoxy resins generallypossess an n value averaging less than about 1.0. Illustrative examplesby standard trade designations of particularly useful commerciallyavailable epoxy resins include: Epi-Rez 508, Epi-Rez 510 and Epi-Rez5661 (Celanese Coatings), ERLA 2256 (U- nion Carbide), ERLA 4617 (UnionCarbide), Epon (Shell), etc.

A variety of epoxy resin curing agents may be employed in conjunctionwith the epoxy resin. The curing or hardening of the epoxy resintypically involves further reaction of the epoxy or hydroxyl groups tocause molecular chain growth and cross-linking. The term curing agent asused herein is accordingly defined to include the various hardeners ofthe co-reactant type. Illustrative classes of known epoxy curing agentswhich may be utilized in the process include aliphatic and aromaticamines, polyamides, tertiary amines, amine adducts, acid anhydrides,acids, aldehyde condensation products, and Lewis acid type catalysts,such as boron trifluoride. The preferred epoxy curing agents for use inthe process are acid anhydrides (e.g., hexahydrophthalic acid anhydrideand methylbicyclo[2.2.lheptene-2,3-dicarboxylic anhydride isomersmarketed under the designation Nadic Methyl Anhydride by the AlliedChemical Company) and aromatic amines (e.g., meta-phenylene diamine anddimethylaniline).

Immediately prior to the coating or impregnation of the graphite ribbonin accordance with the present process, the fibrous bundles optionallymay be surface modified in order to promote optimum adhesion between thefilaments and the thermosetting resin. For instance, the graphite ribbonmay be passed through a gaseous atmosphere according to procedures knownin the art, whereby devolatilization is promoted and the surfacecharacteristics of the ribbon modified. Degassing or devolatilizationmay be performed by techniques such as heating the material whilepassing through a zone containing nitrogen at a temperature of about1,200 C.

In a preferred embodiment of the process when the graphite ribbon iscoated with a solventless system comprising an A-stage thermosettingresin, the coated ribbon may be continuously fed to a heating zone whileretaining the essentially parallel relationship of the multifilamentbundles within the coated ribbon. In such additional heating zone thegraphite ribbon is heated at an elevated temperature and the A-stagethermosetting resin coating is converted to a soft and tacky B-stagethermosetting resin. Such conversion is accomplished while the coatedgraphite ribbon is continuously passed through a heating zone. Thetemperature of the heating zone in which the thermosetting resin isconverted to a B-stage consistency will vary with the particularthermosetting resin utilized. In a preferred embodiment of the inventionthe graphite ribbon bearing a coating of an A-stage epoxy resin ispassed through a heating zone maintained at about 80 to 250 C. for aresidence time of about 3 seconds to about 5 minutes, and preferablyabout 3.5 to 180 seconds. The residence time utilized is generallyinversely proportional to the temperature of the heating zone. In aparticularly preferred embodiment of the invention thefibrous materialbearing a coating of an A-stage epoxy resin is passed through a heatingzone maintained at about 100 to 175 C. for a total residence time ofabout 40 to 180 seconds. Preferred heating zones for use in the processinclude enclosed furnace, and tube furnaces in which the coated graphiteribbon is suspended along the axial center of the furnace. The coatedribbon may also be heated while in sliding contact with a smooth surfaceplaced over a heating element. Such technique is not preferred, however,because of the tendency for resin to build up upon the surface coveringthe heating element and to damage the ribbon passing thereover. It isessential that any heating of the graphite ribbon bearing the B-stagethermosetting resin be terminated while the thermosetting resin presentupon the graphite ribbon is a B-stage thermosetting resin, and thereforebefore a rigid solid C-stage consistency is achieved. Air may beconveniently used as the atmosphere in the heating zone in which anA-stage thermosetting resin is converted to a tacky B-stagethermosetting resin.

Immediately prior to the introduction of the coated graphite ribbon intoa heating zone in which a B-stage consistency is achieved, it isrecommended that any excess resin present thereon be removed. Forinstance, excess resin may be conveniently removed by passage of thecoated fibrous material between a pair of poly tetrafluorethylenerollers which are positioned in a relatively closely spacedrelationship.

The resulting resin impregnated graphite ribbon may be directly used inthe shaping, winding or molding of the fiber reinforced composites, orplaced in storage for future use. The present process enables theexpeditious production of preimpregnated graphite ribbons which possessan extended shelf life. For instance, the epoxy impregnated graphiteribbons commonly may be stored as long as several days at roomtemperature while still retaining a B-stage consistency. If stored underrefrigeration (e.g., at about 0 C.) such ribbons commonly exhibit aconsiderably longer shelf life (e.g., up to about 90 days or more). Theexact shelf life will vary with the thermosetting resin selected.

The resin impregnated graphite ribbons produced in the present processfind particular utility in the produc' tion of high performancestructures which are highly useful in the aerospace industry. Forinstance, impellers, turbine blades, and similar lightweight structuralcomponents may be formed by conventional filament winding, molding, orshaping techniques.

The following examples are given as specific illustrations of theinvention. It should be understood, however, that the invention is notlimited to the specific details set forth in the examples. Reference ismade in the examples to the drawings.

EXAMPLE I An acrylonitrile homopolymer is dry spun to produce a 40 filcontinuous filament yarn, and is hot drawn at a draw ratio of about7.521 to obtain a highly oriented fibrous material having a singlefilament tenacity of about 7 grams per denier. Forty ends of this yarnare then plied to produce 1,600 fil bundles each having a total denierper bundle of about 2,300, and a twist of about 0.5 tpi. The bundles arestabilized (i.e., preoxidized) in air at 278 C. for minutes on acontinuous basis in accordance with the teachings of commonly assignedUS. Pat. application, Ser. No. 865,332, filed Oct. 10, 1969, of KennethS. Burns and William M. Cooper which is herein incorporated byreference. The stabilized bundles are black in appearance, exhibit abound oxygen content of 11 percent by weight as determined by theUnterzaucher analysis, retain their original fibrous configurationessentially intact, and are non-burning when subjected to an ordinarymatch flame.

As shown in FIG. 1, continuous lengths of the bundles l, 2, 3, 4, 5, 6,7, and 8 are provided on rotating bobbins 10, 12, 14, 16, 18, 20, 22,and 24. As the bundles are unwound from the respective bobbins at a rateof 0.25 meter/minute, they are passed to a rotatable slotted or groovedroll 26 with each bundle being individually positioned within one of aplurality of adjacent grooves on the surface of the same and therebyaligned in parallel. The parallel multifilament bundles l, 2, 3, 4, 5,6, 7, and 8 then each pass through adjacent teeth of comb 28 wherebytheir parallel relationship is preserved, and then are looped about aplurality of cylindrical driven rolls 30, 32, 34, 36, and 38 which areprecisionally aligned in parallel. The multifilament bundles ofstabilized acrylic fibrous material while at room temperature (i.e.,about 25 C.) enter and are continuously passed through thecarbonization/graphitization zone 40 which is provided with a nitrogenatmosphere while the bundles remain in an essentially parallelrelationship and in the form of a ribbon. Air is excluded fromcarbonization/graphitization zone 40 by means of a nitrogenoverpressure. Alternatively, air may be excluded fromcarbonization/graphitization zone 40 by mercury seals, or a series ofback diffusion chambers. The parallel relationship of the multifilamentbundles 1, 2, 3, 4, 5, 6, 7, and 8 as they pass over cylindrical roll 38and into the heating zone in which carbonization and graphitization arecarried out is illustrated in FIG. 3.

The carbonization/graphitization zone 40 includes an lnductotherm KCinduction furnace which is equipped with a KW power source. Asillustrated in FIG. 2, a main susceptor 42 formed of graphite having alength of 18 inches, an outer diameter of 2 A inches and an innerdiameter of one-half inch is provided. At the entrance end of mainsusceptor 42 is positioned an auxiliary graphite susceptor 44 having alength of 12 inches, an outer diameter of 1 inch, and an inner diameterof one-half inch. At the exit end of main susceptor 42 is positioned anadditional auxiliary graphite susceptor 46 having a length of 6 inches,an outer diameter of 1 inch, and an inner diameter of one-half inch. Ahollow water cooled copper coil 48 having a coil inner diameter of 5inches and a length of 18 inches substantially encompasses mainsusceptor 42. The copper coil 48 is connected to 20 KW power source 50.The ribbon 52 consisting of 8 parallel fibrous bundles of stabilizedacrylic fibrous material enters the carbonization/graphitization zone 40where it is elevated from room temperature (i.e., about C.) to atemperature of l,400 C. in about 60 seconds during which time it isconverted to a carbonized ribbon consisting of essentially amorphouscarbon. As the carbonized ribbon continues its path through thecarbonization/graphitization zone 40, it is subjected to an increasingand then a decreasing temperature profile with its temperature beingraised from about 1,400 C. to a maximum temperature about 2,900 C.within about seconds. The ribbon is exposed to the maximum temperatureof about 2,900 C. for about 40 seconds during which time the essentiallyamorphous carbon of the carbonized ribbon is substantially converted tographitic carbon. The resulting graphite ribbon is next exposed toprogressively decreasing temperatures through the remaining portion ofthe zone 40, and upon exiting at 54 again assumes room temperature(i.e., about 25 C.). Upon physical testing each bundle within thegraphite ribbon is found to have essentially uniform physical properties(i.e., tensile strength and Youngs modulus).

The graphite ribbon next passes over a plurality of driven cylindricalrolls 56, 58, 60, 62, and 64. The relative speeds of the driven rolls30, 32, 34, 36, and 38 situated before the carbonization/graphitizationzone 40 in relationship to the speeds of driven rolls S6, 58, 60, 62,and 64 situated thereafter are controlled by drive mechanism 166. Therelative speeds of these rolls are adjusted so that a tension of about300 grams is exerted upon each multifilament bundle of the stabilizedacrylic fibrous material as it passes through thecarbonization/graphitization zone 40. V

The resulting graphite ribbon next is passed over a pair of cylindricalidler rolls 68 and 70 as well as about intermediate cylindrical roll 72.After leaving cylindrical roll 70 the graphite ribbon is immersed invessel 74 which contains a solventless system 76 comprising an A-stageepoxy resin by the aid of driven rolls 78, 80, and 82. Tension isapplied to the ribbon by means of a weight attached to intermediatecylindrical roll 72. Dancer arm 73 is connected to the shaft ofintermediate roll 72 and movement of the arm is sensed by aphoto-electric cell (not shown) which actuates driven rolls 78, 80, and82 so that the graphite ribbon is under a constant tension of about 70grams per fibrous bundle while impregnated in vessel 74.

The solventless epoxy resin system contains 100 parts by weight of acondensation product of bisphenol A and epichlorohydrin, 87 parts byweight of hexahydrophthalic acid anhydride curing agent, and 1 part byweight of benzyldimethylamine which serves as an accelerator. The epoxyresin is commercially available from the Celanese Coatings Company underthe designation Epi-Rez 508. The solventless epoxy resin system 76 is ata temperature of 25 C. as the graphite ribbon passes through the same.

The coated graphite ribbon is next passed between a pair ofpolytetrafluoroethylene rollers 84 and 86 having a spacing of 0.011 inchwhere excess resin coating is removed. The essentially parallelrelationship of the bundles within the coated graphite ribbon ismaintained as the ribbon is continuously fed to heating zone 88. As thecoated graphite ribbon is continuously passed through heating zone 88,the A-stage epoxy resin present thereon is converted to a tacky B-stageconsistency and the essentially parallel relationship of the fibrousgraphite bundles within the ribbon is preserved. The heating zone 88 isa forced convection oven wherein the coated graphite ribbon is heated inan air atmosphere at 123 C. for a residence time of 2% minutes. As thecoated graphite ribbon is withdrawn from the heating zone 88 bearing theB-stage epoxy resin coated thereon, it is passed over a pair of idlerrolls 90 and 92 as well as about intermediate roll 94. Tension isapplied to the ribbon by means of a weight attached to intermediate roll94. Dancer arm 95 is connected to the shaft of intermediate roll 94 andmovement of the arm is sensed by a photo-electric cell (not shown) whichactuates the rotation of driven storage roll 96 so that the graphiteribbon is wound upon storage roll 96 ata constant tension of about 50grams per fibrous bundle. The preimpregnated graphite ribbon exhibits ashelf life of about 5 days at room temperature wherein optimumflexibility is maintained,

and of about 90 days while under refrigeration at C.,

and may be wound to form fiber reinforced composites by conventionaltechniques.

EXAMPLE II Example I is repeated with the exception that 0.3 part byweight of l-methylimidazole accelerator is substituted for 1 part byweight of benzyldimethylamine accelerator, and the coated graphiteribbon is heated in heating zone 88 for 2% minutes at 146 C.

EX AMPLE Ill Example I is repeated with the exception that thesolventless epoxy resin contains 100 parts by weight of the condensationproduct of orthophthalic acid and epichlorohydrin which is essentiallythe diglycidyl ester of orthophthalic acid, and 19 parts by weight ofmetaphenylene diamine curing agent. The epoxy resin is commerciallyavailable from the Celanese Coatings Company under the designationEpi-Rez 5661. The

coated graphite ribbon is heated in heating zone 88 for 2 minutes at141C.

EXAMPLE IV Example I is repeated with the exception that a solventthermosetting resin system is applied in vessel 76. The resin systemcontains 100 parts by weight of the condensation product isophthalicacid and epichlorohydrin which is essentially the diglycidyl ester ofisophthalic acid, 39.5 parts by weight of diaminodiphenyl sulfone curingagent, and parts by weight of acetone solvent. The resin impregnatedribbon is heated in heating zone 88 for 2% minutes at 70 C. during whichtime a portion of the acetone solvent is evolved. The resin impregnatedgraphite ribbon is flexible and contains an essentially uncured epoxycomponent. The ribbon may be shaped or molded in an open mold to form acomposite article.

EXAMPLE V Example I is repeated with the exception that a solventthermosetting resin system is applied in vessel 76. The resin systemcontains 100 parts by weight of a condensation product of bisphenol Aand epichlorohydrin which is essentially the diglycidyl ether ofbisphenol A, 32.6 parts by weight diaminodiphenyl sulfone curing agent,1 part by weight boron trifluoridemonoethylamine complex curing agent,and 60 parts by weight methyl ethyl ketone solvent. The resinimpregnated ribbon is heated in heating zone 88 for 10 minutes at 135 C.during which time essentially all of the solvent is evolved, and theresin converted to a B- stage consistency.

EXAMPLE VI Example I is repeated with the exception that themultifilament fibrous bundles which serve as the starting material are acarbonaceous yarn derived from an acrylonitrile homopolymer containingabout 99 percent carbon by weight and exhibiting an essentiallyamorphous X-ray diffraction pattern.

EXAMPLE VII preferred embodiments it is to be understood that variationsand modifications may be resorted to as will be apparent to thoseskilled in the art. Such variations and modifications are to beconsidered within the purview and scope of the claims appended hereto.

Iclaim:

1. A process for the continuous production of a resin impregnatedgraphite ribbon for use in the manufacture of fiber reinforcedcomposites comprising:

a. continuously passing a plurality of substantially uniformmultifilament bundles of a fibrous material capable of undergoinggraphitization while in an adjoining essentially parallel relationshipand in the form of a ribbon having a thickness corresponding to that ofa single multifilament bundle with each bundle being under asubstantially uniform tension through a graphitization zone at atemperature of about 2,000 to 3,1 00 C. and containing an inertatmosphere for a residence time sufficient to substantially convert saidbundles to graphitic carbon while retaining their original fibrousconfiguration essentially intact,

b. continuously feeding the resulting bundles of fibrous graphiticcarbon from said graphitization zone to a coating zone,

c. continuously passing said bundles of graphitic carbon through saidcoating zone while retaining said adjoining essentially parallelrelationship of said bundles and said ribbon configuration having athickness corresponding to that of a single multifilament bundle witheach bundle being under a substantially uniform tension wherein saidribbon is impregnated with a thermosetting resin, and

d. withdrawing the resulting resin impregnated graphite ribbon from saidcoating zone.

2. A process according to claim 1 wherein said plurality ofmultifilament bundles of a fibrous material capable of undergoinggraphitization contain at least about 90 percent carbon by weight andexhibit an es sentially amorphous X-ray diffraction pattern.

3. A process according to claim 1 wherein said multifilament bundles ofa fibrous material capable of undergoing graphitization are derived froma fibrous material selected from the group consisting of anacrylonitrile homopolymer and acrylonitrile copolymers which contain atleast about mol percent of acrylonitrile units and up to about 15 molpercent of one or more monovinyl units copolymerized therewith.

4. A process according to claim 1 wherein said multifilament bundles offibrous material capable of undergoing graphitization are passed throughsaid graphitization zone at a temperature of about 2,400 to 3 1 00 C.

5. A process according to claim I wherein said multifilament bundles arecontinuous multifilament yarns having essentially no twist.

6. A process according to claim 1 wherein said multifilament bundles arecontinuous multifilament yarns having a twist of about 0.1 to 5 tpi.

7. A process according to claim 1 wherein said thermosetting resin is anepoxy resin.

8. A process for the continuous production of a resin impregnatedgraphite ribbon for use in the manufacture of fiber reinforcedcomposites comprising:

a. continuously passing a plurality of substantially uniformmultifilament bundles of a fibrous material capable of undergoinggraphitization while in an adjoining essentially parallel relationshipand in the form of a ribbon having a thickness corresponding to that ofa single multifilament bundle with each bundle being under asubstantially uniform tension through a graphitization zone at atemperature of about 2,000 to 3,l00 C. and containing an inertatmosphere for a residence time sufficient to substantially convert saidbundles to graphitic carbon while retaining their original fibrousconfiguration essentially intact,

. continuously feeding the resulting bundles of graphitic carbon fromsaid graphitization zone to a coating zone,

c. continuously passing said bundles of graphitic carbon through saidcoating zone while retaining said adjoining essentially parallelrelationship of said bundles and said ribbon configuration having athickness corresponding to that of a single multifilament bundle witheach bundle being under a substantially uniform tension wherein saidbundles are coated with a solventless system comprising an A-stagethermosetting resin,

. continuously feeding said coated ribbon from said coating zone to aheating zone while retaining said adjoining essentially parallelrelationship of said bundles within said ribbon,

e. continuously passing said coated ribbon through said heating zonewherein said A-stage thermosetting resin present on said ribbon isconverted to B-stage thermosetting resin while retaining said adjoiningessentially parallel relationship of said bundles within said ribbon,and

f. continuously withdrawing said coated graphite ribbon from saidheating zone while said thermosetting resin present on said ribbon is aB-stage thermosetting resin.

9. A process according to claim 8 wherein said plurality ofmultifilament bundles of a fibrous material capable of undergoinggraphitization contain at least about 90 percent carbon by weight andexhibit an essentially amorphous X-ray diffraction pattern.

10. A process according to claim 9 wherein said multifilament bundles ofa fibrous material capable of undergoing graphitization are derived froma fibrous material selected from the group consisting of anacrylonitrile homopolymer and acrylonitrile copolymers which contain atleast about 85 mol percent of acrylonitrile units and up to about molpercent of one or more monovinyl units copolymerized therewith.

11. A process according to claim 8 wherein said multifilament bundles offibrous material capable of undergoing graphitization are passed throughsaid graphitization zone at a temperature of about 2,400" to 3,100 C.

12. A process according to claim 9 wherein said multifilament bundlesare continuous multifilament yarns having essentially no twist.

13. A process according to claim 9 wherein said multifilsment bundlesare continuous multifilament yarns having a twist of about 0.3 to 1.0tpi.

14. A process according to claim 9 wherein said solventless systemcomprising an A-stage thermosetting resin comprises an A-stage epoxyresin and a curing agent for said epoxy resin.

15. A process according to claim 14 wherein said epoxy resin is acondensation product of bisphenol A and epichlorohydrin.

16. A process for the continuous production of a resin impregnatedgraphite ribbon for use in the manufacture of fiber reinforcedcomposites comprising:

a. continuously passing while in an adjoining essentially parallelrelationship and in the form of a ribbon having a thicknesscorresponding to that of a single multifilament bundle a plurality ofsubstantially uniform multifilament bundles of a stabilized acrylicfibrous material with each bundle being under a substantially uniformtension having a temperature within the range of about 20 to 500 C.which is non-burning when subjected to an ordinary match flame andderived from an acrylic fibrous material selected from the groupconsisting of an acrylonitrile homopolymer and acrylonitrile copolymerswhich contain at least about mol percent of one or more monovinyl unitscopolymerized therewith through a carbonization heating zone providedwith an inert atmosphere in which said bundles of stabilized acrylicfibrous material are raised within a period of about 3 seconds to about10 minutes to a temperature within the range of about 900 C. to about1,600 C. wherein a carbonized ribbon is formed,

b. continuously passing said carbonized ribbon through a graphitizationheating zone provided with an inert atmosphere while retaining saidadjoining parallel relationship of said bundles within said ribbon witheach bundle being under a substantially uniform tension in which saidcarbonized ribbon is heated at a temperature within the range of about2,000 to 3,100 C. for a residence time sufficient to substantiallyconvert said bundles to graphitic carbon,

c. continuously feeding the resulting bundles of graphitic carbon fromsaid graphitization heating zone to a coating zone,

. continuously passing said bundles of graphitic carbon through saidcoating zone while retaining said adjoining essentially parallelrelationship of said bundles and said ribbon configuration having athickness corresponding to that of a single multifilament bundle witheach bundle being under a substantially uniform tension wherein saidribbon is impregnated with a thermosetting resin, and

e. withdrawing the resulting resin impregnated graphite ribbon from saidcoating zone.

17. A process according to claim 16 wherein said multifilament bundlesare continuous multifilament yarns having essentially no twist.

18. A process according to claim 16 wherein said multifilament bundlesare continuous multifilament yarns having a twist of about 0.1 to 5 tpi.

19. A process according to claim 16 wherein said multifilament bundlesof stabilized acrylic fibrous material are derived from an acrylonitrilehomopolymer.

20. A process according to claim 16 wherein said carbonized ribbon iscontinuously passed througlra graphitization heating zone at about 2,400to 3,l C. for a residence time sufficient to convert said bundlesforming the same to graphitic carbon.

21. A process for the continuous production of a resin impregnatedgraphite ribbon for use in the manufacture of fiber reinforcedcomposites comprising:

a. continuously passing while in an adjoining essentially parallelrelationship and in the form of a ribbon having a thicknesscorresponding to that of a single multifilament bundle a plurality ofsubstantially uniform multifilament bundles of a stabilized acrylicfibrous material with each bundle being under a substantially uniformtension having a temperature within the range of about 20 to 500 C.which is non-burning when subjected to an ordinary match flame andderived from an acrylic fibrous material selected from the groupconsisting of an acrylonitrile homopolymer and acrylonitrile copolymerswhich contain at least about 85 mol percent of acrylonitrile units andup to about mol percent of one or more monovinyl units copolymerizedtherewith through a carbonization heating zone provided with an inertatmosphere in which said bundles of stabilized acrylic fibrous materialare raised within a period of about 3 seconds to about 10 minutes to atemperature within the range of about 900 C. to about 1,600 C. wherein acarbonized ribbon is formed,

b. continuously passing said carbonized ribbon through a graphitizationheating zone provided with an inert atmosphere while retaining saidadjoining parallel relationship of said bundles within said ribbon witheach bundle being under a substantially uniform tension in which saidcarbonized ribbon is heated at a temperature within the range of about2,400 to 3,l00 C. for a residence time sufficient to substantiallyconvert said bundles to graphitic carbon,

0. continuously feeding the resulting bundles of graphitic carbon fromsaid graphitization heating zone to a coating zone,

. continuously passing said bundles of graphitic carbon through saidcoating zone while retaining said adjoining essentially parallelrelationship of said bundles and said ribbon configuration having athickness corresponding to that of a single multifilament bundle witheach bundle being under a substantially uniform tension wherein saidribbon is coated with a solventless system comprising an A-stagethermosetting resin,

e. continuously feeding said coated ribbon from said coating zone to aheating zone while retaining said adjoining essentially parallelrelationship of said bundles within said ribbon,

f. continuously passing said coating ribbon through said heating zonewherein said A-stage thermosetting resin present on said ribbon isconverted to B-stage thermosetting resin while retaining said adjoiningessentially parallel relationship of said bundles within said ribbon,and g. continuously withdrawing said coated graphite ribbon from saidheating zone while said thermosetting resin present on said ribbon is aB-stage thermosetting resin.

22. A process according to claim 21 wherein said stabilized acrylicfibrous material is derived from an acrylonitrile homopolymer.

23. A process according to claim 21 wherein said solventless systemcomprising an A-stage thermosetting resin comprises an A-stage epoxyresin and a curing agent for said epoxy resin.

24. A process according to claim 22 wherein said A- stage epoxy resin isa condensation product of bisphenol A and epichlorohydrin.

2. A process according to claim 1 wherein said plurality ofmultifilament bundles of a fibrous material capable of undergoinggraphitization contain at least about 90 percent carbon by weight andexhibit an essentially amorphous X-ray diffraction pattern.
 3. A processaccording to claim 1 wherein said multifilament bundles of a fibrousmaterial capable of undergoing graphitization are derived from a fibrousmaterial selected from the group consisting of an acrylonitrileHomopolymer and acrylonitrile copolymers which contain at least about 85mol percent of acrylonitrile units and up to about 15 mol percent of oneor more monovinyl units copolymerized therewith.
 4. A process accordingto claim 1 wherein said multifilament bundles of fibrous materialcapable of undergoing graphitization are passed through saidgraphitization zone at a temperature of about 2,400* to 3,100* C.
 5. Aprocess according to claim 1 wherein said multifilament bundles arecontinuous multifilament yarns having essentially no twist.
 6. A processaccording to claim 1 wherein said multifilament bundles are continuousmultifilament yarns having a twist of about 0.1 to 5 tpi.
 7. A processaccording to claim 1 wherein said thermosetting resin is an epoxy resin.8. A process for the continuous production of a resin impregnatedgraphite ribbon for use in the manufacture of fiber reinforcedcomposites comprising: a. continuously passing a plurality ofsubstantially uniform multifilament bundles of a fibrous materialcapable of undergoing graphitization while in an adjoining essentiallyparallel relationship and in the form of a ribbon having a thicknesscorresponding to that of a single multifilament bundle with each bundlebeing under a substantially uniform tension through a graphitizationzone at a temperature of about 2,000* to 3,100* C. and containing aninert atmosphere for a residence time sufficient to substantiallyconvert said bundles to graphitic carbon while retaining their originalfibrous configuration essentially intact, b. continuously feeding theresulting bundles of graphitic carbon from said graphitization zone to acoating zone, c. continuously passing said bundles of graphitic carbonthrough said coating zone while retaining said adjoining essentiallyparallel relationship of said bundles and said ribbon configurationhaving a thickness corresponding to that of a single multifilamentbundle with each bundle being under a substantially uniform tensionwherein said bundles are coated with a solventless system comprising anA-stage thermosetting resin, d. continuously feeding said coated ribbonfrom said coating zone to a heating zone while retaining said adjoiningessentially parallel relationship of said bundles within said ribbon, e.continuously passing said coated ribbon through said heating zonewherein said A-stage thermosetting resin present on said ribbon isconverted to B-stage thermosetting resin while retaining said adjoiningessentially parallel relationship of said bundles within said ribbon,and f. continuously withdrawing said coated graphite ribbon from saidheating zone while said thermosetting resin present on said ribbon is aB-stage thermosetting resin.
 9. A process according to claim 8 whereinsaid plurality of multifilament bundles of a fibrous material capable ofundergoing graphitization contain at least about 90 percent carbon byweight and exhibit an essentially amorphous X-ray diffraction pattern.10. A process according to claim 9 wherein said multifilament bundles ofa fibrous material capable of undergoing graphitization are derived froma fibrous material selected from the group consisting of anacrylonitrile homopolymer and acrylonitrile copolymers which contain atleast about 85 mol percent of acrylonitrile units and up to about 15 molpercent of one or more monovinyl units copolymerized therewith.
 11. Aprocess according to claim 8 wherein said multifilament bundles offibrous material capable of undergoing graphitization are passed throughsaid graphitization zone at a temperature of about 2,400* to 3,100* C.12. A process according to claim 9 wherein said multifilament bundlesare continuous multifilament yarns having essentially no twist.
 13. Aprocess according to claim 9 wherein said multifilament bundles arecontinuous multifilament yarns having a twIst of about 0.3 to 1.0 tpi.14. A process according to claim 9 wherein said solventless systemcomprising an A-stage thermosetting resin comprises an A-stage epoxyresin and a curing agent for said epoxy resin.
 15. A process accordingto claim 14 wherein said epoxy resin is a condensation product ofbisphenol A and epichlorohydrin.
 16. A process for the continuousproduction of a resin impregnated graphite ribbon for use in themanufacture of fiber reinforced composites comprising: a. continuouslypassing while in an adjoining essentially parallel relationship and inthe form of a ribbon having a thickness corresponding to that of asingle multifilament bundle a plurality of substantially uniformmultifilament bundles of a stabilized acrylic fibrous material with eachbundle being under a substantially uniform tension having a temperaturewithin the range of about 20* to 500* C. which is non-burning whensubjected to an ordinary match flame and derived from an acrylic fibrousmaterial selected from the group consisting of an acrylonitrilehomopolymer and acrylonitrile copolymers which contain at least about 85mol percent of one or more monovinyl units copolymerized therewiththrough a carbonization heating zone provided with an inert atmospherein which said bundles of stabilized acrylic fibrous material are raisedwithin a period of about 3 seconds to about 10 minutes to a temperaturewithin the range of about 900* C. to about 1,600* C. wherein acarbonized ribbon is formed, b. continuously passing said carbonizedribbon through a graphitization heating zone provided with an inertatmosphere while retaining said adjoining parallel relationship of saidbundles within said ribbon with each bundle being under a substantiallyuniform tension in which said carbonized ribbon is heated at atemperature within the range of about 2,000* to 3,100* C. for aresidence time sufficient to substantially convert said bundles tographitic carbon, c. continuously feeding the resulting bundles ofgraphitic carbon from said graphitization heating zone to a coatingzone, d. continuously passing said bundles of graphitic carbon throughsaid coating zone while retaining said adjoining essentially parallelrelationship of said bundles and said ribbon configuration having athickness corresponding to that of a single multifilament bundle witheach bundle being under a substantially uniform tension wherein saidribbon is impregnated with a thermosetting resin, and e. withdrawing theresulting resin impregnated graphite ribbon from said coating zone. 17.A process according to claim 16 wherein said multifilament bundles arecontinuous multifilament yarns having essentially no twist.
 18. Aprocess according to claim 16 wherein said multifilament bundles arecontinuous multifilament yarns having a twist of about 0.1 to 5 tpi. 19.A process according to claim 16 wherein said multifilament bundles ofstabilized acrylic fibrous material are derived from an acrylonitrilehomopolymer.
 20. A process according to claim 16 wherein said carbonizedribbon is continuously passed through a graphitization heating zone atabout 2,400* to 3,100* C. for a residence time sufficient to convertsaid bundles forming the same to graphitic carbon.
 21. A process for thecontinuous production of a resin impregnated graphite ribbon for use inthe manufacture of fiber reinforced composites comprising: a.continuously passing while in an adjoining essentially parallelrelationship and in the form of a ribbon having a thicknesscorresponding to that of a single multifilament bundle a plurality ofsubstantially uniform multifilament bundles of a stabilized acrylicfibrous material with each bundle being under a substantially uniformtension having a temperature within the range of about 20* to 500* C.Which is non-burning when subjected to an ordinary match flame andderived from an acrylic fibrous material selected from the groupconsisting of an acrylonitrile homopolymer and acrylonitrile copolymerswhich contain at least about 85 mol percent of acrylonitrile units andup to about 15 mol percent of one or more monovinyl units copolymerizedtherewith through a carbonization heating zone provided with an inertatmosphere in which said bundles of stabilized acrylic fibrous materialare raised within a period of about 3 seconds to about 10 minutes to atemperature within the range of about 900* C. to about 1,600* C. whereina carbonized ribbon is formed, b. continuously passing said carbonizedribbon through a graphitization heating zone provided with an inertatmosphere while retaining said adjoining parallel relationship of saidbundles within said ribbon with each bundle being under a substantiallyuniform tension in which said carbonized ribbon is heated at atemperature within the range of about 2,400* to 3,100* C. for aresidence time sufficient to substantially convert said bundles tographitic carbon, c. continuously feeding the resulting bundles ofgraphitic carbon from said graphitization heating zone to a coatingzone, d. continuously passing said bundles of graphitic carbon throughsaid coating zone while retaining said adjoining essentially parallelrelationship of said bundles and said ribbon configuration having athickness corresponding to that of a single multifilament bundle witheach bundle being under a substantially uniform tension wherein saidribbon is coated with a solventless system comprising an A-stagethermosetting resin, e. continuously feeding said coated ribbon fromsaid coating zone to a heating zone while retaining said adjoiningessentially parallel relationship of said bundles within said ribbon, f.continuously passing said coating ribbon through said heating zonewherein said A-stage thermosetting resin present on said ribbon isconverted to B-stage thermosetting resin while retaining said adjoiningessentially parallel relationship of said bundles within said ribbon,and g. continuously withdrawing said coated graphite ribbon from saidheating zone while said thermosetting resin present on said ribbon is aB-stage thermosetting resin.
 22. A process according to claim 21 whereinsaid stabilized acrylic fibrous material is derived from anacrylonitrile homopolymer.
 23. A process according to claim 21 whereinsaid solventless system comprising an A-stage thermosetting resincomprises an A-stage epoxy resin and a curing agent for said epoxyresin.
 24. A process according to claim 22 wherein said A-stage epoxyresin is a condensation product of bisphenol A and epichlorohydrin.